Edexcel Chemistry A2 Unit 5 ~ Wednesday 19th June 2013 (Now Closed) Watch

Poll: How pumped up are you for this exam?-(warning)-(bad jokes arene this poll!)
"Titanium-I'm not going to corrode (even at high temperatures)" (A*) (22)
16.67%
"Benzene's my middle name, give me the paper in a week and I'll ace it!" (A) (27)
20.45%
"Yeah, I'm fairly electrophillic (positively charged) about the exam" (B) (27)
20.45%
"I'm in the middle of the salt bridge, but I will pass-eventually" (C) (21)
15.91%
"I'm feeling rather electroNegative about this exam" (D) (18)
13.64%
"Benzene, what's that?" (E) (6)
4.55%
"Chemistry, what's that?" (F) (11)
8.33%
This discussion is closed.
AS01
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#541
(Original post by LeaX)
Does anyone know if we need to know the names and structures of different amino acids? Such as glycine, alanine, cysteine, phenylalanine, and aspartic acid. Thank you in advance.
No we dont
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LeaX
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(Original post by AS01)
No we dont
Oh thank god for that haha. Thanks.
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AS01
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(Original post by LeaX)
Oh thank god for that haha. Thanks.
remembering that would be daunting lol!
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Mollymod
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Yeah but after using some of them so often, you can probably remember that Glycine is the simplest one, with a H as the R group in it.

Although that's the only one I know thus far XD
Won't bother learning them either really.
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MustaphaMond
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(Original post by AS01)
I applied to St.George's, Queen Mary, Sheffield and Birmingham. Did you get offers?
Woo! Another medic!
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David Tennant
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#546
(Original post by AS01)
I applied to St.George's, Queen Mary, Sheffield and Birmingham. Did you get offers?
Yeah, Got an offer from Sheffield...Not sure how though!
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Mollymod
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(Original post by David Tennant)
Yeah, Got an offer from Sheffield...Not sure how though!
Congratulations

Ummm with Vanadium's oxidation states, how do you know which oxidising agent to use to oxidise it from +2 to +4 (as an example) or reduce it from +5 to +3 etc

and do we have to know the equations for the oxidation/reduction reactions of vanadium? I know we do for Copper/Chromium compounds
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posthumus
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(Original post by Mollymod)
Congratulations

Ummm with Vanadium's oxidation states, how do you know which oxidising agent to use to oxidise it from +2 to +4 (as an example) or reduce it from +5 to +3 etc

and do we have to know the equations for the oxidation/reduction reactions of vanadium? I know we do for Copper/Chromium compounds

Wait so you can't use the oxidisting agent... potassium manganate (VII) all the time ???
and what equations do we need to remember


Also a quick question - In the Facer book... if I come across anything to do with DNAs and blood, I can just skip it right ?

Thanks
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Mollymod
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(Original post by posthumus)
Wait so you can't use the oxidisting agent... potassium manganate (VII) all the time ???
and what equations do we need to remember


Also a quick question - In the Facer book... if I come across anything to do with DNAs and blood, I can just skip it right ?

Thanks
What do you mean? You have to know that blood needs to maintain a pH so there's a buffer involved with pH regulation in blood.

DNA, I don't really remember much coming up about DNA to do with Chemistry. There's a bit about protein synthesis but I dont know what you're referring to here.

Nope, you have to use zinc for some of them, and Nitric acid for others; I dont know off the top of my head. Chemguide has the stuff somewhere.

And like [Cu(H2O)6]2+(aq) +2OH-(aq) -> [Cu(H2O)4(OH)2] (s)
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posthumus
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(Original post by Mollymod)
What do you mean? You have to know that blood needs to maintain a pH so there's a buffer involved with pH regulation in blood.

DNA, I don't really remember much coming up about DNA to do with Chemistry. There's a bit about protein synthesis but I dont know what you're referring to here.

Nope, you have to use zinc for some of them, and Nitric acid for others; I dont know off the top of my head. Chemguide has the stuff somewhere.

And like [Cu(H2O)6]2+(aq) +2OH-(aq) -> [Cu(H2O)4(OH)2] (s)
I am utterly clueless lol

Thank-you for the reply
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jojo1995
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(Original post by Mollymod)
What do you mean? You have to know that blood needs to maintain a pH so there's a buffer involved with pH regulation in blood.

DNA, I don't really remember much coming up about DNA to do with Chemistry. There's a bit about protein synthesis but I dont know what you're referring to here.

Nope, you have to use zinc for some of them, and Nitric acid for others; I dont know off the top of my head. Chemguide has the stuff somewhere.

And like [Cu(H2O)6]2+(aq) +2OH-(aq) -> [Cu(H2O)4(OH)2] (s)

vo2^+ +2h+ + -> vo^2+ + h20


vo^2+ + 2h+ -> v3+ h20


basically i think you look at the different e values in the data booklet .... but i think Zn can reduce vanadium from 5+ all the way to 2+ === this is according to chem guide


http://www.chemguide.co.uk/inorganic.../vanadium.html
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posthumus
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(Original post by jojo1995)
vo2^+ +2h+ + -> vo^2+ + h20


vo^2+ + 2h+ -> v3+ h20


basically i think you look at the different e values in the data booklet .... but i think Zn can reduce vanadium from 5+ all the way to 2+ === this is according to chem guide


http://www.chemguide.co.uk/inorganic.../vanadium.html
Would you be able to explain why that is ?

Zinc has full orbitals
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Mollymod
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(Original post by jojo1995)
vo2^+ +2h+ + -> vo^2+ + h20


vo^2+ + 2h+ -> v3+ h20


basically i think you look at the different e values in the data booklet .... but i think Zn can reduce vanadium from 5+ all the way to 2+ === this is according to chem guide


http://www.chemguide.co.uk/inorganic.../vanadium.html
So if the E value is higher than the E cell of the Vanadium half equation, it can reduce it?

I mean, let's say

VO3- +5e + 6H+ --------> 3H2O + V E Cell's 1.1V
and Zn -----> Zn2+ + 2e E Cell's 1.12V

would that mean the Zn can reduce the VO3- because it has a bigger E Value or am I completely mistaken?
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posthumus
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(Original post by Mollymod)
So if the E value is higher than the E cell of the Vanadium half equation, it can reduce it?

I mean, let's say

VO3- +5e + 6H+ --------> 3H2O + V E Cell's 1.1V
and Zn -----> Zn2+ + 2e E Cell's 1.12V

would that mean the Zn can reduce the VO3- because it has a bigger E Value or am I completely mistaken?
That should be right ? If it is feasible (that way round) meaning the electrode potential is positive, then that means the reaction would happen.

Since VO3- is getting reduced and Zinc oxidized, that makes zinc the reducing agent ?

EDIT: And are you sure both the Electrode potentials will be positive, or did you make those values up ?
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jojo1995
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(Original post by posthumus)
Would you be able to explain why that is ?

Zinc has full orbitals


Doc4.odt

in the attatchment you can see that the e potential for the reduction of vanadium is more positive than that of zn - so the reaction between the vanadium and zinc will occur

zinc will lose its 4s electron so the 3d electrons arent affected
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jojo1995
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(Original post by Mollymod)
So if the E value is higher than the E cell of the Vanadium half equation, it can reduce it?

I mean, let's say

VO3- +5e + 6H+ --------> 3H2O + V E Cell's 1.1V
and Zn -----> Zn2+ + 2e E Cell's 1.12V

would that mean the Zn can reduce the VO3- because it has a bigger E Value or am I completely mistaken?
isnt the e value for the reduction of zn2+ -> zn is -0.76 ?
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posthumus
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(Original post by jojo1995)
Doc4.odt

in the attatchment you can see that the e potential for the reduction of vanadium is more positive than that of zn - so the reaction between the vanadium and zinc will occur

zinc will lose its 4s electron so the 3d electrons arent affected
If its lost only its 4s electrons then how would Vanadium go from +5 state to +2 ? and the 4s is full anyway ? so wouldn't it be stable anyway.

Thanks for that file but How do I work out the Electrode cell potential? First I multiply the top by 2 right ? & then I switch the bottom one (change -0.76 to +0.76)

So when adding the 2 up I get Ecell = 2.76 V ?
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posthumus
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(Original post by jojo1995)
isnt the e value for the reduction of zn2+ -> zn is -0.76 ?
I think she made them up the second equation would be positive because her equation is the other way around...

Also sorry I'm like whining today because I really don't understand anything... and I have so much to learn !
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jojo1995
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(Original post by posthumus)
I think she made them up the second equation would be positive because her equation is the other way around...

Also sorry I'm like whining today because I really don't understand anything... and I have so much to learn !

aww don't worry, im the same ... its the way we learn i guess

(Original post by posthumus)
If its lost only its 4s electrons then how would Vanadium go from +5 state to +2 ? and the 4s is full anyway ? so wouldn't it be stable anyway. --- no you can remove electrons from the 4s if its full just not the 3d if its full--- not exactly sure why but =, it happens with the other d blocks too ie transition metals

Thanks for that file but How do I work out the Electrode cell potential? First I multiply the top by 2 right ? & then I switch the bottom one (change -0.76 to +0.76)yep you reverse it so you change it to a positive and then you never multiplu elecrode potentials btw im not sure if you did but they remain the same even if you multiply the equations==== you multiply to work out the overall equations though - ewlectrons have to be the same in each equation to balance

So when adding the 2 up I get Ecell = 2.76 V ?
no see below

(i) 2VO2+(aq) + 4H+(aq) + Zn(s) ==> 2VO2+(aq) + 2H2O(l) + Zn2+(aq)

EØreaction = EØreduction – EØoxidation = +1.00 – (–0.76) = +1.76V


i got this from : http://www.docbrown.info/page07/transition03V.htm


"Zinc can reduce the vanadium through each of these steps to give the vanadium(II) ion." - from chem guide --=- i think this means that you would add zinc after each stage, you wouldnt do it all together at once... youd have to do each stage individually, one after another
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Mollymod
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(Original post by jojo1995)
isnt the e value for the reduction of zn2+ -> zn is -0.76 ?
Yeah I made it up off the top of my head for the sake of the question but nevermind
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